Regulatory studies of L-glutamate dehydrogenase from Trypanosoma cruzi epimastigotes.

1. The specific activity of NADP-dependent L-glutamate dehydrogenase (GDH) from T. cruzi epimastigotes increased from 0.7 at early log-phase to 1.4 mumol/min/mg of protein at the stationary phase. 2. When T. cruzi cells were incubated in the presence of L-glutamate (0.08%), the GDH had a specific activity of 2.2, much higher than that of cells incubated in the presence of D-glucose (0.08%), which was 1.2 mumol/min/mg of protein. 3. The specific activity of NADP-dependent GDH from cells incubated in the presence of L-glutamate did not vary when the cells were treated with cycloheximide (100 ng/ml) or chloramphenicol (0.5 mg/ml). 4. The activity of the NAD-dependent GDH did not change in any of the situations described above. 5. AMP, ADP, ATP, citrate, isocitrate, oxaloacetate, fructose-1,6-diP, pyruvate, L-proline and L-arginine did not have any effect on the NADP-linked GDH activity. Product inhibition studies were done on the latter GDH activity.